I've look around on the forum for a report on this issue but didnt find any.

I'm using Maya2015 and arnold 1.1.0.4
Basically applying BA_illum_RGB_Shadow on a plane+sphere test setup with any arnold light, which has the arnold specific light samples above 1, will create artifacts.

A workaround is up'ing Camera (AA) samples in render globals, keeping samples on light on 1, however that is not ideal.